Circular Housing Structure for Sealed Electric Linear Actuators
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Solution Overview
Problem
Existing electric linear actuators with gear mechanisms suffer from power loss, increased motor size, and power consumption due to sliding contact, and have sealability issues with noncircular housing configurations, which impair durability and strength.
Innovation Solution
A circular cross-sectional configuration for the housing with a cylindrical gear containing portion and abutment surfaces, along with a belt speed reduction mechanism and rolling bearings, enhances sealability, rigidity, and strength by reducing the housing's opening areas and using a sealing member between abutment surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gear mechanism is used to transmit rotational power to the ball screw mechanism, then the rotational speed of the electric motor is reduced, but power loss increases and motor size increases
Solution Approach 1:
The patent replaces the traditional gear mechanism with a direct-drive configuration where the electric motor's output shaft is directly coupled to the ball screw mechanism. This eliminates the intermediate gear transmission stage, thereby removing the associated sliding contact friction and power loss while maintaining the speed reduction function through the ball screw's mechanical advantage.
Solution Approach 2:
The patent extracts and removes the gear mechanism from the power transmission system, keeping only the essential ball screw mechanism for motion conversion. This simplification eliminates the idler gear and associated sliding contact portions, reducing power loss and allowing for a more compact motor design.
2Reliability
If a two-piece housing with noncircular cross-section is used to contain the gear mechanism and ball screw mechanism, then the components are protected, but sealability deteriorates and strength decreases
Solution Approach 1:
The patent changes the housing cross-sectional shape from a noncircular (pear-like) configuration to a circular configuration. This circular cross-section provides more uniform stress distribution under load, enhancing the housing's strength and rigidity while improving sealability at the joint between housing pieces.
Solution Approach 2:
The patent merges the functions of protecting both the gear mechanism and ball screw mechanism within a single integrated housing structure. By eliminating the need for separate protective enclosures, the housing design achieves better structural integrity and sealing while maintaining component protection.
3Force
If the housing opening area is reduced to improve sealability, then sealability improves, but access for maintenance and assembly becomes difficult
Solution Approach 1:
The patent divides the housing into two separable pieces (first housing and second housing) that can be assembled and disassembled. This segmentation allows for easy access to internal components for assembly and maintenance while maintaining a compact overall structure with improved sealability when the pieces are joined together.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves sealability, durability, and strength of the electric linear actuator by reducing power loss and motor size, while maintaining efficiency and compactness, and reduces the amount of sealing agent required.
Implementation Method 1
a ball screw mechanism (7) for converting the rotational motion of the electric motor (M) to axial linear motion of a driving shaft (6), comprising a nut (18) formed with a helical screw groove (18a) on an inner circumference and a screw shaft (10) formed with a helical screw groove (10a) on an outer circumference, inserted into the nut (18) via a large number of balls (17)
Implementation Method 2
the nut (18) is supported by rolling bearings (20, 20) mounted on the first housing (2a) rotationally but axially immovably
Implementation Method 3
a sealing member (29) is interposed between the abutment surfaces (21, 22) of the first and second housings (2a, 2b)
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An object of the present invention is to provide an electric linear actuator intended to improve the sealability of the housing and the durability of the actuator by changing the cross-sectional configuration of the two-piece housing from a noncircular configuration to a circular configuration. According to the present invention, there is provided an electric linear actuator comprising a housing; an electric motor mounted on the housing; and a speed reduction mechanism for reducing the rotational speed of the electric motor and transmitting the rotational power of the electric motor to a ball screw mechanism for converting the rotational motion of the electric motor to the axial linear motion of a driving shaft; the ball screw mechanism comprising a nut formed with a helical screw groove on its inner circumference and supported by rolling bearings mounted on the housing rotationally but axially immovably; and a screw shaft coaxially integrated with the driving shaft, formed with helical screw groove on its outer circumference corresponding to the helical screw groove of the nut, inserted into the nut via a large number of balls, and supported axially movably but not rotationally relative to the housing characterized in that the housing comprises a first housing on which the electric motor is mounted and a second housing to be abutted against an end face of the first housing, that the first housing is formed with a cylindrical gear containing portion for containing the speed reduction mechanism, that part of an end of the gear containing portion of the first housing extends radially inward to form a bottom portion for covering the speed reduction mechanism, and that the bottom portion of the first housing and the second housing are formed with abutment surfaces respectively.